I have a character here that you can use if you want to. You may or may not have Street Grimoire, so you might need to get the book to explain some of it to your GM.
https://docs.google.com/spreadsheets/d/1uoF8tnSnA9Hbvf3aJVUKNxcAoJyJ1L0xmSycbQ70qqQ/edit#gid=0I would recommend against a "dumb" character. Sure, you can build one that isn't the super smart college educated guy, but if you're correctly roleplaying the 1 Logic, 1 Charisma guy, he's a complete idiot that no one really wants around since he's more a nuisance than anything else. If you want a character who is built using only the SR5 books, I'll list one below. Just note, that it may not be the most optimized character. Add whatever name, Alias, and backstory you want. Also, he's not big, because he's a dwarf.
-- Priorities --
Metatype C (Dwarf)
Attributes A
Magic B
Skills D
Resources E
-- Karma Expenditure --
50 Total
-19 in Qualities
-10 for 20,000 nuyen
-10 to raise Edge to 2
-6 for Skills
-5 for Contacts
0 Left
-- Attributes --
Body 7
Agility 4
Reaction 4 (7)
Strength 8 (9)
Willpower 3
Logic 3
Intuition 5
Charisma 3
Edge 2
Essence 6
Magic 7
Initiative - 12 + 4d6
Physical Condition Monitor - 12
Stun Condition Monitor - 10
Physical Limit - 11
Mental Limit - 5
Social Limit - 5
-- Qualities --
Adept
Thermographic Vision - Racial
+2 Dice to resist Pathogens and Toxins - Racial
Exceptional Attribute - Magic (-14 Karma)
Mentor Spirit - Shark (-5 Karma)
Astral Beacon (+10 Karma)
Combat Junkie (+7 Karma)
Social Stress (+8 Karma)
-- Skills --
Perception 6 (+2 Visual) - Dice pool of 11 (13)
Sneaking 5 (+2 Urban) - Dice pool of 9 (11)
Throwing Weapons (+2 Blades) - Dice pool of 10 (12)
Unarmed Combat (+2 from Mentor Spirit) [+3 from Improved Ability) - Dice pool of 15
Ettiquette 1 - Dice pool of 4 (might not do much, but you never know)
Running 1 - Dice pool of 10
Swimming 1 - Dice pool of 10
-- Knowledge/Language Skills --
English N
Japanese 6
High Threat Response Times 6 - Street
Seattle Streets 6 - Street (substitute wherever your campaign is)
Shadow Community 4 - Street
-- Gear --
Armor Jacket w/ Nonconductivity 6 - 2,500 nuyen
30 Shuriken - 750 nuyen
Rating 4 Fake SIN (John Doe, substitute whatever name you want) - 10,000 nuyen
Rating 4 Fake License (Shuriken) - 800 nuyen
Rating 4 Fake License (Registered Adept) - 800 nuyen
Transys Avalon Commlink - 5,000 nuyen
3 Meta Link Commlinks - 300 nuyen (throwaway links)
1 Gold Credstick, 3 Silver Credsticks - 160 nuyen
Capacity 4 Glasses w/ Flare Compensation, Image Link, Low-Light Vision, and Vision Magnification - 1,425 nuyen
Low Lifestyle (Apartment), 1 month - 2,400 nuyen
Remaining Money - 1,865 + (3d6 x 60) nuyen
-- Adept Powers --
Killing Hands - Free from Mentor Spirit
Improved Reflexes 3 - 3.5 PP
Combat Sense 2 - 1.0 PP
Improved Physical Attribute (Strength) - 1.0 PP
Improved Ability (Unarmed Combat) 3 - 1.5 PP
-- Contacts --
Fixer: Connection 4, Loyalty 3
Street Doc: Connection 2, Loyalty 5